function User(name) {
  this.name = name;
}

User.prototype = {
  show() {
    return this.name;
  }
};

let xj = new User("向军");
console.log ( User.prototype);
console.log(xj.constructor === User.prototype.constructor); // true
console.log(xj.constructor === User); // false
console.log(xj.constructor === Object); // true